the rotating anode xray tube

Question 1

explain the process of x-ray production in the rotating anode tube

Answer 1

• the tungsten filament produces electrons through thermionic emission in the cathode
• a tube voltage is applied across the X-ray tube which accelerates electrons towards the anode
• the anode is positive so attracts the negatively charged electrons
• the electrons hit the anode tube with a maximum KE, they hit the tungsten target embedded in the anode block and interact to produce x-rays
• the focusing cup repels negative electrons away from the coil due to the space charge effect.

Question 2

heat dissipation

Answer 2

• rotating anode helps to distribute heat across a larger surface area
• oil surrounds the tube and conducts heat away to the outer casing and the air

Question 3

Bremsstralung

Answer 3

• electromagnetic radiation is produced by the deceleration of a charged particle when deflected by another charged particle
• the positive electric charge of the nucleus exerts a force on a passing negative electron
• the KE of the electron is converted into a photon
• the energy of the photon is relative to the amount of change in the KE of the electron (hf=e1-e2)
• the proximity of the electrons path to the nucleus will determine how much energy is lost from the electron and imparted into the x-ray photon
• continuous spectrum

Question 4

e-max

Answer 4

the point where all of the KE of an electron has been converted to x-radiation

Question 5

characteristic

Answer 5

• produced when a high energy particle collides with an inner shell elcetron, ejecting it from its shell
• The kinetic energy of the electrons, accelerated from the filament, is so great that inner shell electrons can be liberated by ionisation
• This will only occur if the kinetic energy of the incident electron (the electron from the filament) is greater than the binding energy of the target electron
• The incident electron will continue on its travels, but with much less speed
• produces a line spectrum